Synergistic brightener combination for amorphous nickel phosphorus electroplatings

Abstract

Leveling of amorphous nickel-phosphorus electroplating is achieved by the combined synergistic action of a class II brightener and an organic acid having the formula R--COOH wherein R is hydrogen, alkyl having 1-5 carbon atoms, NH 2 CH 2 --, CH 3 CHOH--, HOCH 2 --, or ClCH 2 --. The bright, leveled, amorphous nickel-phosphorus coating may be made brighter by overplating with chromium, or other metals, to produce an object (such as cutlery, watch bezels and the like) having the desired properties.

What is claimed is: 
     
       1. A method producing a leveled electroplated coating comprising the steps of: (a) adding to an electroplating bath including nickel and phosphorus ions as the primary constituents thereof, at least one compound selected from the group consisting of unsaturated organic compounds that are class II brightening agents, and at least one organic acid in an amount between one part in 60 and one part in 10, based on the volumes of the organic acid and the bath, respectively selected from the group having the formula   R--COOH      wherein R is alkyl having 1-5 carbon atoms, hydrogen, NH 2  CH 2  --, CH 3  CHOH--, HOCH 2  --, or ClCH 2  --; the amount and type of unsaturated organic compound class II brightening agent being selected so as to cooperate with said organic acid to enhance leveling;     (b) immersing an object to be electroplated, and removing the object once electroplated, so that it has at least one surface thereof with leveled amorphous nickel-phosphorus electroplated thereon, and   (c) overplating the leveled amorphous nickel-phosphorus coating with chromium.   
     
     
       2. A method as recited in claim 1 wherein the organic acid is selected from the group consisting of acetic acid and hydroxyacetic acid. 
     
     
       3. A method as recited in claim 2 wherein the bath is maintained at a temperature of between about 75° C.-95° C. 
     
     
       4. A method as recited in claim 3 wherein electroplating further practiced by maintaining the current density between about 25-400 ma/cm 2 . 
     
     
       5. A method as recited in claim 4 wherein the pH of the bath is maintained between about 0.5-2. 
     
     
       6. A method as recited in claim 5 wherein the object immersed has an electrically conductive surface on which amorphous nickel-phosphorus is electroplated. 
     
     
       7. A method as recited in claim 2 wherein step (a) is further practiced by adding a surface active agent to the bath. 
     
     
       8. A method as recited in claim 2 wherein the object immersed has an electrically conductive surface on which amorphous nickel-phosphorus is electroplated. 
     
     
       9. A method as recited in claim 1 wherein electroplating is further practiced by maintaining the current density between about 25-400 ma/cm 2 . 
     
     
       10. A method as recited in claim 1 wherein electroplating is further practiced by maintaining the pH of the bath between about 0.5-2. 
     
     
       11. A method as recited in claim 1 wherein electroplating is practiced by maintaining the bath at a temperature of between about 75° C.-95° C. 
     
     
       12. A method as recited in claim 1 wherein step (a) is further practiced by adding a surface active agent to the bath. 
     
     
       13. A method as recited in claim 12 wherein the surface active agent is alkoxylated linear alcohol. 
     
     
       14. A method as recited in claim 1 wherein the object immersed has an electrically conductive surface on which amorphous nickel-phosphorus is electroplated. 
     
     
       15. A coated object comprising: a base surface of electrically conductive material;   a level coating of amorphous nickel-phosphorus on said surface; and   a bright overplating of chromium on said level amorphous nickel-phosphorus coating.   
     
     
       16. An object as recited in claim 15 wherein the coating of nickel-phosphorus is between about 25-1000 microinches thick. 
     
     
       17. A method producing a leveled electroplated coating comprising the steps of: (a) adding to an electroplating bath including nickel and phosphorus ions as the primary constituents thereof, at least one compound selected from the group consisting of unsaturated organic compounds that are class II brightening agents, and at least one organic acid in an amount between one part in 60 and one part in 10, based on the volumes of the organic acid and the bath, respectively selected from the group having the formula   R--COOH     wherein R is alkyl having 1-5 carbon atoms, hydrogen, NH 2  CH 2  --, CH 3  CHOH--, HOCH 2  --, or ClCH 2  --; the amount and type of unsaturated organic compound class II brightening agent being selected so as to cooperate with said organic acid to enhance leveling;     (b) immersing an object to be electroplated, and removing the object once electroplated, so that it has at least one surface thereof with leveled amorphous nickel-phosphorus electroplated thereon, and   (c) overplating the amorphous nickel-phosphorus coating with a material selected from the group consisting of gold, white gold, titanium nitride, and silver.   
     
     
       18. A method as recited in claim 17 wherein the organic acid is selected from the group consisting of acetic acid and hydroxyacetic acid. 
     
     
       19. A method as recited in claim 18 wherein step (a) is further practiced by adding a surface active agent to the bath.